Believe it or not the northland greens and the mid eastern north coastal ones do not need any out of the norm cooling. I have keep and breed both of these forms as a kid. In Gisborne we experience relatively waarm weather a good part of the season and only a seldom frost in some winters. In cairns though waterrat, you are probably right and you would have to think that they would needed to be keep indoors in the summer at the very least.
I both hate and love these threads on the NZ green gecko's. On one hand I would give up snakes in a heart beat to keep these but knowing it isn't going to happen here legally any time soon, just teases me.
By the way cobber, I couldn't find reference on goggle earth for the spot over there I mentioned.
Cheers Dave